It is often desired to perform tests utilizing instruments of various sorts which have at least a portion or an element thereof disposed in structures subjected to and being in a flow facing relationship with high velocity or high temperature flows, i.e., high total enthalpy flows. This occurs, for example in Magneto-Hydro-Dynamic (MHD) generators, in jet engine or missile probing, in some tests conducted in wind tunnels or in some tests and probings conducted on flying vehicles. Many elements of these instruments are adversely affects by high temperature or by temperature changes, and in order to function properly, these elements should be maintained at a fairly stable, low temperature.
In particular, when an element, such as a sensor of an instrument is disposed adjacent to the leading edge or to the tip of an object submerged in a high total enthalpy flow, its heating rate is very high. However, these are desired positions for many purposes such as turbulence measurements in an incoming flow, unperturbed by the probe, or for sensing flow properties such as temperature and temperature non-uniformities or particle velocities, or for infra-red detection of heat in heat seeking missiles and the like.
Utilizing a blunt and thick leading edge or tip, which lowers the heating rate, sometimes adversely affects the fluid flow and the aerodynamic properties of the probe or of the device or flying vehicle which carries it.
There is known in reconnaisance planes a side or bottom facing, shallow recess wherein a camera is disposed behind a glass window, generally disposed in the fuselage. The interior of these recesses has a very uneven heating rate. The more uneven the heating rate, the less efficient the functioning of the window and the instruments therein.